1. Field of the Invention
Apparatus and method are provided for aligning spaced-apart elongated elements, such as tubulars, equipment or instruments used in wells, such that the angle between the spaced-apart elements measured perpendicular to the axis of the elements can be determined or fixed. The apparatus and method are particularly suited for aligning the elements in directional core barrels used for determining the orientation of cores of rock cut from boreholes.
2. Description of Relevant Art
In drilling wells and obtaining information about the rock which the well has penetrated, it is often necessary to measure or fix the relative angular position of various elongated tubular members used in well operations. Visual sighting methods are used on the surface of the earth before the elongated tubular members are lowered into a well. In U.S. Pat. No. 4,141,153, a bottom hole survey apparatus is described wherein alignment between a reference indicator line within a survey instrument and an axially displaced external slot in a mule shoe is provided by visual sighting elements, or "peep holes." Visual sighting is used to align the elongated members of the apparatus, so that the members are oriented in a known direction when they are placed in a well. In U.S. Pat. No. 2,088,539, a means of orienting deflecting tools in wells is described. A telescope and a target are used as sighting members to align one element of the apparatus with another.
In the method of cutting cores or samples of rock from a borehole and measuring the orientation of the rock with respect to survey instruments run into the well, as described in U.S. Pat. No. 2,735,652, it has been common practice to align the various elements of the apparatus by using a telescope attached to one element and a sighting bar attached to another element. U.S. Pat. No. 3,059,707 also discloses use of a telescopic member for aligning markings which are axially displaced in an apparatus for orienting cores. In the patents cited, the telescope and an object used for sighting are attached to tubular members using clamping means which allow the sighting devices to be positioned with respect to a reference line on a tubular member. Other rudimentary techniques of alignment have been used, such as attaching a carpenter's level in a direction perpendicular to the axis of the elements and adjusting the angle until a level position is indicated on each element. Each of these methods depends on ambient light levels high enough to observe the aligning objects and the accuracy of each depends on the care and skill of the operator.